In general, a distributed architecture system may be defined as a system comprising multiple electronic modules interconnected by a communication bus. The block diagram of FIG. 1 depicts an example of a distributed architecture system, as applied to an automotive supplemental restraint system (SRS). Referring to FIG. 1, the SRS 10 comprises a central control module 12, and a number of crash sensor modules 14, occupant sensor modules 15, and ignitor modules 16 located remote from the central module 12, but coupled in parallel to central module 12 via a communication bus 18 comprising wires 18a and 18b. In a typical mechanization, the central control module 12 collects and processes input data from the various crash sensor modules 14 and occupant sensor modules 15, signals selected ignitor modules 16 to deploy one or more supplemental restraints, and diagnoses the ignitor modules 16 for proper functionality. Inter-module communications to support these functions can be achieved by modulation of the bus voltage and/or bus current. In a particularly advantageous implementation, the bus wire 18b defines a reference potential, the central module 12 communicates with the remote modules 14-16 by modulating the voltage on bus wire 18a with respect to bus wire 18b, and the remote modules 14-16 communicate with the central module 12 by modulating the current in bus wire 18a: this permits concurrent central-to-remote and remote-to-central communications, effectively doubling the communication capability (bandwidth) of the bus 18. However, modulating the bus current produces un-intended modulation of the bus voltage due to bus resistance, particularly in systems where the remote modules are resistively coupled to the bus 18 to isolate the bus 18 from short circuit failures in the remote modules.
Possible solutions to the above-described problem include one or more of the following: maximizing the amplitude of voltage modulation, minimizing the amplitude of current modulation, and minimizing the remote module coupling resistance. However, increasing the amplitude of voltage modulation increases the radiated emissions; decreasing the amplitude of current modulation reduces signal-to-noise ratio and susceptibility to radiated emissions; and reducing the remote module coupling resistance degrades fault tolerance and increases transmitter power dissipation during short circuit conditions. Accordingly, what is needed is a distributed architecture system that enables reliable, high-bandwidth, and fault-tolerant inter-module bus communication without the aforementioned drawbacks.